Pressure regulation



Feb. 26, 1935. A. J. oTTo 1,992,881'

PRESSURE REGULATIQN Filed March 12, 1934 2 Sheets-Sheet l Jmaentor IIT SA )L n Feb. 26, v1935.

A. J. o'rTo 1,992,881

PRESSURE REGULATION Filed March l2, 1934 2 Sheets-Sheet 2 (Ittomegs xmotion in an opening direction.

Patented, Feb. 26, i935 UNITED f s'rii'rlasl f'fPATENT loF-Flcr; V.

.a'nlssnaa REGULATION IJ. th, Milwaukee, Wis., assigner to fff/olmsonService Company, Milwaukee, Wil.,

a corporation of Wisconsin Application March 12, 1934, Serial No.715,206.

unbalanced, and hence require thel exercise oft,

considerable force to bring abouttheir initial As typical of valves ofthis class may be men" tioned valves of the poppet type includingbalancing means controlled by a4 small but unbalanced pilot valve, thepilot valve having a deil'nite seating tendency. These valvesarepeculiarly desirable hecausethey combine the characteristics of freemotion while flow occurs with the highlyuseful characteristic of adefinite seating tendency when closed.

One characteristic of the invention is the use vof two motor means,which may be described as the main actuating motor and a secondary orbooster motor. The main motor operates toshift the pressure-reducingvalve throughout its operative range, and the booster motorfunctionsmerely to carry the load of producing .the initialopeningmovement of the valve and is thereafter inactive. The simplestway to accomplish this is to limit the motion of the booster motor to avery small range, and so arrange it that it is in th ast i relation withthe valve-actuating means when the valve'is completely closed.

Another feature of the invention is the control of the secondary orbooster motorin response to the condition of, energization` of the, mainmotor, When the main motor is completely inert `the booster motor isinert. vWhen the main motor is energizedsliglrtly the booster motor iscom- 1 pletely energized so that it goes through its complete operativecycle, prefjerably before the main motor is energized suiliciently toshift the valve at all. As a result of such an arrangement the mainmotor -opera'tes to .actuate the valve under uniform conditions ofbalance and can` therefore.' function precisely.

Further details of the invention involve the' use of a pneumatic relayoperatedin'eresponse to pressures created by iiow through the pressure-A. reducing valve to establish a variable pressure in the main motor. Inthis way progressive regulation of theflow-controlling'l valve of apeculiarly smooth and reliable character mayzbe Y Another feature of theinvention is the -of a pneumatic relay responsive to the pressureconditionin the main motor to energize and de-energize the secondarymotor. By using a relay of the main motor to shift the valve at all.Since v the motion of the secondary motor establishes a balancedcondition of the valve, the main motor becomes operative upon acompletely balanced valve, and actuates that valve smoothly through itsentire regulative range.

The inventionis susceptible of embodiment in a number of specicallydifferent forms, two of `which will be described. One shows theinvention embodied bythe use of pressure motors and relaysextensively'usedin the temperature-regulat- 20 ing art. The other showsthe possibility of omitting one relay in certain cases.

In the accompanying drawings.-

Fig. 1 is a view partly in diagrammatic velevation and partly insection, showing the essential elements of the device. The flowregulating valve isshown in closed condition.

Fig. 2 is an axial section through one of the iluid pressure relays.

Fig. 3 -is a detail The invention has been successfully used for thepurpose of supplying low pressures am from 35.

ahigh pressure main to a low pressure receiver or other receptacle. Theinvention may'be used 'in conjunction with apparatus for(ie-superheating steam inthe low pressure receiver, but since .thede-superlieating apparatus functions inde-A pendently of the 'pressurereducing apparatus, and is not essential to the operation ofthe'pressure reducing valve mechanism, it is not illus- .Y trated. Itshould be expresslyunderstood, however, that there is Anot in theconstructionQ45.

or operative characteristics of the pressure reducing mechanismwliionwouldrpreclude the use of such a de-superheating mechanism ifdesired.` Furthermore, the invention is' in nowise limited to reductionof pressure of steam, as it might be used with any fluid, particularlyexpansible iiuids., Y

- While compressed air will be referred to in the descrptionas themotive uid used in the main, and secondary motors, other suitablepressure u fluids may be substituted as occasion mand. l

y Refer first to Figs. 1 and 2.

In the drawings, 6 represents a high pressure main here assumed to be asteam main and 7 represents the body of a pressure-reducing valve.'I'his valve is illustrated as typical and no novelty is here claimedfor the specific construction of the valve. The body y7 is connected toan elbow 8 which conducts the steam at reduced pressure to a lowpressure container or receiver 9. The body 7 of.the valve is providedwith a seat 11 for la valve element 12 of the poppet type. The valveelement 12 has a pilot and flow-controlling element 13 which is oftapered form, and which terminates rat its lower end in a balancing heador piston 14 working in a cylindrical chamber formed as an extension ofthe valve body 7. The space within`cylinder-15 above the piston head 14is in communication with the discharge (low pressure side) of the valvearound vthe pilot 13. The space below the piston 14 -is connected by wayof the small axial passage 16 with the seat 17 of an unbalanced pilotvalve 18 of the poppet type.

The valve 18 is of much smaller area than the now-controlling valve 12'but nevertheless, when closed, is subjected to substantial seatingpressure. vThe opening of the valve 1 8'subjects the space below thepiston 14 to supply pressure arriving through the high pressureconnection 6, butsince the effective area of the piston 14 is made-equalto the effective area of the valve 12,the pening may deof the valve.18places the valve 12 in a condition of static balance. Valve 18 has astem 19 which :works in a collar 21 xed in the upper end of the stem 19is drawn up it first unseats valve 18 to balance valve 12, and thenrenters into thrust engagement with collar 21 and serves as a. conn`valve 12. The parts are so arranged that when head 24 guided in a guidepassage 25. Thisis supfV ported by a yoke 26 carried by the bonnet. Alever 27 pivoted to cross head 24 and to a radius link 28 which in turnis pivotedto yoke 26, offers means-for actuating stem l9 andconsequently both the pilot valve 18 andthe main flow-controlling valve12. l; determinate closing tendency is imparted to the valve structureby means. Aof weights 29`hung on the outer end of the lever 27. A lever31pivoted at 32 to any suitable x'ed support 33 is connected by a link34 with the 1ever 27. `Mounted on' support 33 is a base 35 for the mainvalve-actuating motor which will be recognized as structurally similarto motors-usedn for'actuating steam' valves and dampers in thetemperature regulating art. This motor includes a base-plate 36angularly adjustable on a vertical axis with reference to base 35, acup-shapedcap cap 37 closed at theiruppenend and sealed at their lowerend to the nember 36.`

The motive pressure for actuating this motor g arrives by way ofthefpipe connection 39,v and the pressure acts in the space between vthebellows 38 and the cap 3 7 so that upon rise: of pressureV the movingelement of the motor is forced down- `Ward. This moving elementcomprises a stem 41 A37, and metallic bellows 38j enclosed within-theV.movable -end lof `the bellows and reacts against 'one arm59` of abell-crank whose other arm is inindicated as composed of two alinedcompression springs 43 and 44 which encircle the stem 41 'and reactbetween the head 42 and a spring seat 40 threaded on the upper end ofbase 35 (see Fig. 3).

It is important to observe at this point that if the springs 43 and 44are under moderate compression when the motor is inert the stem 41 willnot start downward motion until a definite and determinate pressure isestablished in the motor.

ever, alight spring could be used. The push rod '49 of themotorterminates at its lower end in a.

beveled thrust plunger 52 which engages' the lever 31 nearits end, andAwhich is limitedin' its downward motion by a stop-plate 53 which may beadjusted by means of the screws 54. The

.adjustment issuch that the push rod 49 can move downward only theYshort distance necessary to swing lever 31 far enough to unseat thepilot Valve 18.

It will be observed that lever 31 is not cor- 30 nected withr the thrustheadv 52Y so that it may turn independently of any motion of) thesecondary motor. From this fact it follows that as soon as the pilotvalve has been opened sufliciently to balance the main valve, the entirecontrol of the mainyalve is taken over by the main motor.v

Any suitable means responsive to pressure in the low pressure receiver 9might be used to establish a variable operating pressure inthe mainmotor, `but in the present casethe use of a modifled form of the relaydevice shown in the Otto and Otto patent, No. 1,500,260 dated July 18,A1924 is illustrated.

The patent above identified shows a relay which produces progressivelyvariable pressure in a branch pipe inV response to progressivevariations in' temperature. The thermally responsive element controls aleak/port. In the present device the leak port is controlled by a valveresponsive to variations in pressure in the receiver 9.

Referring to Fig. 1, a connection 55 leads from' the receiver 9 to thechamber 56 in which is mounted a metallic bellows 57 closed atV itslower end. A thrust rod 58 is connected to the closedA dicated at 61.This bell-crank is pivoted` at 62 and has its range of motion fixed byadjustable 'I'he'uid pressure acting on the bellows 57 is resisted byl acoiled compressionspring- 64 which reacts between the arm 59 of thebell-crank and an adjustable spring seat 65. The upper end of arm 61 ofthe bell-crank is"connected by a link 66 with a rocking lever 67 .whichis in thrust engage'ment with the valve member 68, sometimes upward by`a compression spring structure here- ;ture of the ttd patent. However,in the interest called a lid, for'a leak port 69.

It would' perhaps suiilce to say that the leak port 69 and the lid 68.just described correspond g to the leak port 30 and valve 31 of the Ottopat.- ent, and control a relay generally indicated in Fig. 1 of thepresent application 'by the reference I numeral 71,' such relayconforming tothe struc-' Adevice.A A supply pipe 72 conductsiluid underpressure, ordinarily compressed air, to the device. It passes throughtwo distinct paths. First, the port 73 which leads past the throttling'needle valve 74 to the space -between the cover 75 and a exiblediaphragm 76. This space is connected by a port 77 and pipe 78 with theleak port 69. The capacity of the leak port slightly, exceeds the' flowcapacity past the throttling needle valve 74 so that variable throttlingof the leak port 69 will establish a variable control pressure in thespace above the diaphragm 76. A second and smaller diaphragm 79' carriesat its center a hub member 81 which is in thrust relation with 'dl-Aaphragm 76 for the reason that the space between the two diaphragms isvented to atmosphere at 82. An exhaust port leads axially through thehub 81 and then laterally to; the space between the two diaphragms.This. port is indicated generally by the numeral 83 and its lower endserves as the exhaust seat for a combined admission and exhaust valve84. The valve 84'also has a supply seat at 85, the seat being formed inthe body 71. A branch-passage 86 leads from supply. con- `nection 72 tothis'valve.

diaphragm v79 to balance the pressure acting in'.I

ward on diaphragm 76. At such time the'valve 84 seals against both theseats above described'. The throttling of the port 69 thereforeestablishes in the .spacegbeneath diaphragm 79 a variable pressure whichis connected by way'of port 87 and pipe 39 (see Fig. 1) to the mainpressure motor. From the above description it will be obvious that. aspressure in the receiver 9 rises the leak port 69 will be progressivelyopened. Conse-A quently, the pressure in the branch line 39 will beprogressively lowered, the plunger 41 of the main motor will move upwardprogressively, and the valve 12 willvbe "progressively closed. Converseaction takes place on fall of pressure in the receiver 9. I

The apparatus so far described would operate the valve 1'2satisfactorily throughout its entire operative range, but would notfurnish the force necessary to unseat the valve 12 without iirstestablishing in the main motor an undulyheavy pressure. .Theestablishment of such a vpressure would cause .the governor to huntbadly. To overcome this defect, the secondary motor is connected so asto be fully energized as soon as a very slight pressure is developed inthe main motor, preferably pressure not lquite. suflicient to overcomethe initial stress in the springs 43 and 44.. i

The means for energizing the, secondary motor is another relayconstructed according 4to the Otto patent above identiiiedandfunctionally Avery similar to the relay .and pressure actuated valvealready Ldescribed. In appearance it is Isomewhat different because thepressure responsive element here responds'to air pressure, and thereforecan be'closely associated with the relay structure, whereas the steamoperated bellows 57 was necessarily isolated from the relay structure toavoid the harmful eiectslof heat.

This relay structure has a' base 91 essentially similarto the base 71,and receives air under pressure through a branch of the supply .pipe72.` This air flows through a port 93 past a throttling needle valve 94to the space between a plate-95' and a diaphragm 96. The space betweenplate 95 and diaphragm 96 is vented by a leak port 97 at a rate which,when the leak port is fully opened, slightly exceeds the rate of flowpast the throttling valve 94. A

It will be observed that the parts so described lconiormfcloselyin-structure, and are identical' in function, with the parts 7l to 77.To simplify A the description it will sufce to apply reference numerals99 to 107 to'the parts corresponding functionally with the parts 79 to87. In other words, similar parts in the two structures are similarlynumbered, the differential between the numbers of the two series beingtwenty. There is nopipe corresponding to the pipe 78 of Fig. 2 for the.reason that this connection is made through 'a port in the base 91.

The pressure responsive device corresponding to the bellows 57 is adiaphragm 108 clamped against the forward side of the plate 95 by acover 109. 'I'he space in frontnf diaphragm 108 is `vented to theatmosphere, the space to the i rear of the diaphragm is connectedby aport lll .with a branch of pipe 39, and consequently fwith the interiorof the main motor space between cap 37 and bellows 33.' Guided in thefront plate 109 is a thrust member` 112 whichv reacts against an arm 113pivoted to base 91 at 114. This arm is drawn inward against the thrustmember 112 by a coiled tension spring 115 and at its end carries athrust screw 116A which bears on one arm of a bell-crank lever 117. Thisbell-crank lever is pivoted at lland carries a valve 119 yco-acting withthe leak port 97. A Weight 121 intended to be typical of any yieldingmeans, urges the belicrank in a `direction to seat valve 119 upon leakport 97* and thus close the leak port. A loading spring 122 having anadjustable threaded spring seat 123 resists outward motion of the thrustmember 112, so that when the diaphragm 108 is 4forced outward andoverpowers spring 122 it will swing lever 113 in a direction to permitvalve 119 to close. The space to the rear of diaphragm 99 is connectedby port 107 and connecting pipe stated. With the understanding thatthestatey l ment of pressures. has no limiting significance, it isassumed that highpressure steam is delivered through the main 6 at 200pounds gage, and that the pressure to be maintained in the receiver 9 is140 pounds. So far as this invention is concerned itis'immaterialwhether the steam in the drum is or is not de-superheated by othermeans. The possibility of using other apparatus so far as the presentinvention is concerned is expressly stated.

It will be assumed that, in accordance with the usual practice,compressed air is `supplied to pipe l 72 at a pressure of approximately15 pounds gage. 'The relay indicatedgenerally by the numeral 71 istherefore capable of establishing in the main motor a pressure which'varies between atmospheric pressure and q15 pounds gage. The

'I'he bellows 57 are of such area,`and the effective stress of theopposing spring 64 is such, that within the governing range ofpressuressin thev receiver 9 the bellows57 will move the leak 68 throughits operative range and thus cause the.,

relay 71 to respond through its operative range.

The stress on the spring 122 and the area of the n diaphragm 108 are sochosen that a variation of pressure in the pipe 39 and consequently inthe main motor between atmospheric pressure andx a few ounces per squareinch gage, will cause the relay mounted onv base 91 to move through. itsentire range. From thisl it follows that when the main motor is atatmospheric the secondary motor will be at atmospheric pressure, andwhenthe main motor is subjected to a pressure of a few ounces per squareinch gage, the secondary .motor will be subject to a .pressure of poundsgage, the maximum pressure available in the pneumatic system.

Assuming that the pressure in the receiver 9 is so high that the valve12 is completelyl closed and the pilot-valve 18 is closed, under suchcondition the bellows 57 must have moved the leak valve 68 sufficientlyto open leak port 69 completely, thus venting the pressure on thediaphragm 76 fasterl than it can be built up by the supply of pressurefluid past the needle valve ,74. Under these con- .ditions pressure inthe line 39 will be vented and the pressure on the bellowsmotor 38 willbe substantially atmospheric. Similarly, the relay structure mounted inbase 91 will functionl to es-` tablish a substantially atmosphericpressure on the secondary motorv bellows 4 8. The closing o! valve 12will result ultimatelyin a decrease of pressure in the receiver 9 sothat the spring 64 will partially overpower bellows 57. 'I'his will movevalve 6810 'throttle partially the outflowA through the leak port 9, thepressure acting on the upper or front face of the diaphragm 76 willrise, the diaphragms 76 and 79 will move downward (inward), and throughcoaction with the combined inlet and exhaust valve84 will estab' lish abalancing or related pressure on the rear face of diaphragm 79. Thispressure iscommunicated through the port 87 and pipe 39 to the yspring122.

working space above bellows /38 in the main motor. Initially thispressure may not be sumcientg to overpower the stress in springs 43, 44,but

e space at the rear of diaphragm 108, this diaphragm will be forcedoutward against the resistance oi 4As explained, the Aparts are soadjusted that the rulting motion of valve 119 in a direction to throttleport'97 will establish practically'the full available pneumatic pressureinthe pipe 125; and consequently inthe working space above the.

bellows 48 ot thesecondary motor. This motor immediately moves throughits complete operative range,and in 'sfo doing shifts lever 31 iustrfarenough to unseat the pilot valve 18' and put the main now-controllingvalve 12 in a balanced condition. The apparatus is Vnow conditioned fora smooth progressive control in reSDOXlSe to variations of pressure intheworking space above the bellows38.

'It be obvious Qthat the rsecondary motor will .not permit the pilotvalve 18 to close until the pressure acting on the main motorbellows 38falls to such a low value that the valve '12 is closed. Preferably, thesecondary motor allows the pilot valve to close as nearly simultaneouslywith the closure`of valve 12 as is practically possible. The closing ofthe pilot valvethrows the main valve out of balance and ensuresadeilnite seating pressure on the main pilot valve which will preventinjury to the valve resulting from leakage or wire drawing.

A simplified embodiment doing away with the "second relay and using amore powerful second-V ayqnotor. is iuustrated in Fig. 4. In this ngurethe parts identical with parts in Fig. 1 are given similar numbers withthe subscript a. The parts in Fig. 1 which are identical in Fig. 4 arethose numbered 8 to 44 and 52 to 87 both inclusive. The structureofFig.'4 contains no parts analogous to the parts numbered 91 to 125l bothinclusive.

Instead of the small auxiliary motor used in Fig. 1, a large motorcomparable in size with the main motor is used. Itcan be of anynecessary size. 'Ihus instead of the parts 45-51, there is a motor base45u carrying disc 46s, cap 47h, bellows 48s, closed at their upper end,and push 4rod 49h with thrust head 51h. Springs 43s andl 44s are usedand are adjustable by spring seat 40s similar to the parts 40s, 43 and44.. The line 39. is connected directly with both'motor vhousings 37sand 47s instead of being connected with the main motor housing and thesecond relay.

The springs 43., '44. are more heavily stressed initially than thfesprings 43s, 44s, so that when both motors are subjected to a givenpressure the diaphragm 48 responds through the limited range\. permittedit substantially when diaphragm 3 8 neutralizes the stress of springs' 43., 43h. Thus as before, the auxiliary motor shifts the pilot valve.-puts themain valve in balance and relinquishes control to the mainmotor.

The modiaed structure is simpler, but is less sensitive and somewhatslower in action. The

secondary relay when used saves air, speeds up response and causes thesecondary motor torespond'to a very low pressure established by the nrstrelay. y

The specific mechanism disclosed in Figs. l and 2 of this applicationlhas been used successfully and'is preferred for commercial'reasons, butthe fact is recognized thatbrcad operative principles are involved, andthat the invention is notjlimited necessarily to the use of the relayvstructures illustrated, or evento the use of relay structures at all.In regulating the valve 12 in response to pressures in the lowgpressurelreceiver 9 the ilrs't essential, according to the invention, is a motorwhich will actuate the valve progressively through its operative rangein response to variations in the pressure to be maintained, inconjunction with some motor means inert when the. main motor is inertand rendered active throughs.

main'motor to assume the load of the initial open-` ing movement of .thevalve. Various arrangementmin addition to the modification illustrated,

range upon the initial energization ot the will accomplish this resultand fall within thef intended broadfseope of th'e 1. The -c oxnliinationof a flow-regulating valve freely movable through Aits operative range.but oilerlng greater'resistace to initial motion fron closed-condition;a main motor for shifting said valve through its operative range; asecondary present invention.

motor capable of dissipating said greater resist-J '15 ance wif-houta'ectingthe motion of the' valve "scr Y l J through its operative raxkegmeansH responsive establish a pressure in the booster motor suilltopressures created by flow\thro h -said valve cient to overcome saidinitial resistance.

and sewing variably toenergize saidmain motor; 9. The combination of aflow-regulating valve .and means responsive to energizationandvde-enof atype substantially balanced through its op-AA ergization of the mainmotor and serving to erlerative range, such balance being established ingize and le-energize the secondary motor. the closed condition of thevalve by the shift- 2. The combination denedinclaim 1`,in.which \`in\gof a pilot valve against substantial rresistboth motors. are of theiiuid pressure operated ance and de-energiration of the main motoris asen- 1 variable flii pressure to shift such valve through sitivepressure-multiplying relay valve mechaits operative Y e; a secondpressure motor connism. nected to open said pilot valve when the second3. 'Ihe combination dened inclaim 1', inwhich motor is subjected topreure; pressure responf 'the secondary motor acts to dissipate saidgreat-- sive means subject to pressures created by ilow er resistance byactuating a pilotV valve which' through the flow-regulating valve andarranged functions to put the flow-regulating valve in a balancedcondition when open and insan unb ancedcondition when closed.

4. 'Ihecombination-of a flow-regulating valve ireely movablel throughsits operative range but oifering resistance to initial motion fromclosed condition; a booster motor arranged to force said valve fromclosed condition without affecting the motion of the valve through theremainder of its range; a main motor for shifting the valve through itsoperative range; pressure responsive means vsubject to pressurescreated4 by ilow through said v alve and serving variably to energizesaid main motor; and meansresponsive to energization and de-energizationof the main motor and serving to energize and de-energiz'e the booster'motor.

' 5. The combination defined in claim 4, in which both motors are of thefluid pressure operated type, and the means responsive to energizationand cle-energizat'ionof the main motor is a sensitivevpressure-multiplying relay valve Y, said main motor and serving to ventsaid motor when the. main-motor is vented and to loir pressure in sure;means responsiveto pressures created mechanism.

6. The. combination or a iiow controlling valve 'having a substantiallyuniform resistance-to motion through its operative range and a greaterresistance to motion at one limit or its range; *a main i motorconnected to shift said valve progressively in response to variations ofa motive-fluid p by now through said valve and arranged to establishrelated motive-huid pressures in said motor; a secondary motor capableof dissipating said greater resistance; and means subject to pressure insaid main motor and 'responsive to conditions therein at the time ofsuch greater resistance, to render the secondary motor active.

7. 'I 'he combination deiined in claim 6, in which the secondary motoris ofthe fluid pressure operated type and the means subject to pressurein said main motor comprises a sensitive presai sure-multiplying relaycontrolling the pressure in such secondary motor. Y 8. The combinationoi a flow-regulating valve of a type substantially balanced through itsoperative range but having` a substantial resistance to initial openingmotion; a main pressure motor 'connected to actuate said valve .andresponsive `to' variable fluid pressure to shift said valve through itsoperativev range;a booster pressure motor arranged to' assist said mainmotor only through the range of substantial lresistance tovalvesopenins; pressure 'responsive valve -means subject to pressurescreated by flow' through said gow-regulating valve and arranged toestablish related fluid pressures in said main motor; and a fluidpressure relay responsive to pressure in booster to establish relatediluid pressures in the main pressure motor; and ailuid pressure relayIeSDOI-VPy sive to pressure in said main motor and serving to vent thesecond motor when the main motor l i a main pressure motor connected toactutype. and the meansl responsive to energization atetldow-controlling valveand responsive to of a type substantially4balanced through its operative range but having a substantialresistance to initial opening motion; a mainl pressure motor connectedto actuate said valve and responsive to variable fluid pressure to shiftsaidV valve through its operative range; a booster pressure motorarranged to assist said main motor only through the range ofsubstantialA resistance to valve-opening; pressure responsive valvemeans subject to pressures created by flow through said flow-regulatingvalve and arranged to establish related uuid pessures in said main motorand booster motor; and means for causing said motors to operateserially. i

11. The combination of a flow-regulating valve of a type substantiallybalanced through its op# erative range but having a substantialresistance to initial-opening motion; a main pressure motor connected toactuate said valve and responsive to variable uid kpressure to shiftsaid valve through its operative range; a booster pressure motorarranged to assist said main motor only through the range of substantialresistance to valve-opening; pressure responsive valve means subject topressures created by flow through said flow-regulating' valve andarranged to establish related fluid pressures in said main motor andbooster motor; and means comprising loading means for at least one ofsaid motors, for causing said motors to operate serially. y

12. The combination of a dow-regulating valve freely movable through itsoperative range but offering greater resistance to initial motion fromclosed condition; a main motor for shifting said valve through itsoperative range; a secondary motor i capable of dissipating said greaterresistance without affecting the motion of the valve through itsoperative range; means responsive to pressures created by flow throughsaid valve and serving variably to energize said motors; and means forrendering said motors effective serially.

s i3, The combination of a flow-regulating valve freely movable throughits operative range butv ouering greater resistance to initial motionfrom closed condition; valve through. its operative range; a secondarymotor capable, 'of dissipating greater resistance without ailecting themotion of the .valve through its operative range; means responsive to4pressures created byqow through said valve and `serving variably toenergize said motors; and

meanscomprisingaloadingmechanismforthe a main motor for shifting saidoffering resistance to initial motion from closed condition;l a boostermotor arranged to force said Y valve from closed condition Withoutaiecting the motion of the valve through the remainder of its range; amain motor for shifting the valve through its operative range; andpressure responsive means subject to pressures created by ow throughsaid valve and serving to energize variably both motors.

to respond serially.

` 15. The combination of a How-regulating valve freely movable throughits operative range but offering resistance to initial motion fromclosed condition; a booster motor# arranged to force said valve fromclosed condition without a'ecting the motion of the valve through .theremainder of its range; a main motor for shifting the valve through itsoperative range; pressure responsive means subject topressures createdby flow through said valve and serving to energize both motors; andmeans for causing said motors Y. ARTHUR J. OTTO;

